At yesterday’s close, shares of Jenny Craig Weight Loss Centers on the New York Stock Exchange were up a whopping 37 percent.

The stock closed at 3 — up 11/16 per share.

The news that Lewinsky will star in a series of Jenny Craig TV ads, while touting an impressive 31-pound weight loss, also had phones at the diet center’s locations across the nation ringing off the hook.

“In the past two days, we’ve been getting more calls from potential clients after they heard that Monica is our spokeswoman,” said a worker at Jenny Craig on Third Avenue in Manhattan.

Media analysts say Lewinsky’s high profile — despite her link to Sexgate — should ultimately be a bonanza for the company.

“You never know how the public will respond — but initially, I think it’s a brilliant move,” said Jack Feuer, Adweek’s media editor.

“It seems like a good marriage of brand and celebrity.”

And it may come just in time to give Jenny Craig a much-needed face lift.

It currently operates 527 company-owned and 79 franchised weight-loss centers across the United States, as well as 110 company-owned and 37 franchised centers in Australia.

That’s about 65,000 clients here and 26,000 in foreign markets.

Lewinsky’s participation comes just months after the company reported major losses.

For the three months ending Sept. 30, revenues fell 16 percent, to $71.5 million, for a net loss of $3.8 million.

The revenues reflected a decrease in active participants, decreases in franchise centers in operation, and less demand for the company’s products.

In the new Lewinsky ads, which debut on ABC Sunday night, the previously portly pepperpot — who once tipped the scales at 223 — gushes about the Jenny Craig weight-loss program.

The 26-year-old Greenwich Village resident — who scandalized the nation with her Oval Office sex romps with President Clinton — is reportedly being paid $10,000 by Jenny Craig for each pound she loses.